The present invention relates generally to lubricant seals, and more particularly refers to a lubricant seal which permits the controlled leakage of lubricant fluid therethrough.
The invention is intended for use in the lubrication of rotating or reciprocating members which are subject to very severe ambient conditions, i.e. where very high temperatures or abrassive environments are involved, and is specially designed for lubricating valve stems in internal combustion engines.
As it is well known, the valves used in internal combustion engines control communication of the intake or exhaust manifolds with the combustion chamber, in which temperatures of 1000.degree. C. and more are developed. Since any lubricant oil exposed to such temperature would inevitably burn, seals have been used in the past to prevent the lubricant from passing into the combustion chamber.
However, the known seals block almost completely the leakage of lubricant oil therethrough and, as a consequence, it has been the general practice to provide a substantial clearance between the valve stems and the respective bushings to avoid the possibility of seizures due to the different expansion rates of the stems and bushings, and the virtual absence of lubrication in the lower portion of the stems. These relatively large clearances and the premature wear of the bushings due to the lack of proper lubrication eventually caused knocking and an irregular and unreliable operation of the engine.